Investigate/figure out path for demo instance's unexpected high usage

[daguar]

Interestingly we're getting something like 10-20 balance checks on our demo # a day.

Ideally we'd want these users to be using the normal service for a bunch of reasons (the big one being that at least some people are texting in from outside California, and so it doesn't work for them.)

[daguar]

One solution: make this instance ONLY allow balance checks for the demo EBT #, and otherwise direct people to a different phone # to use.